Fix HiDPI issues on secondary screen

Reset the renderer and texture on display scaling change.

FIXME problem with texture (see FIXME in code)

Co-authored-by: Louis Kruger <louisk@gmail.com>

app/meson.build

@@ -116,9 +116,6 @@ conf.set('DEFAULT_LOCK_VIDEO_ORIENTATION', '-1')  # -1: unlocked
 # overridden by option --bit-rate
 conf.set('DEFAULT_BIT_RATE', '8000000')  # 8Mbps
 
-# enable High DPI support
-conf.set('HIDPI_SUPPORT', get_option('hidpi_support'))
-
 # disable console on Windows
 conf.set('WINDOWS_NOCONSOLE', get_option('windows_noconsole'))
 

app/src/scrcpy.c

@@ -109,9 +109,10 @@ static int
 event_watcher(void *data, SDL_Event *event) {
     (void) data;
     if (event->type == SDL_WINDOWEVENT
-            && event->window.event == SDL_WINDOWEVENT_RESIZED) {
-        // called from another thread, not very safe, but it's a workaround!
-        screen_render(&screen);
+            && event->window.event == SDL_WINDOWEVENT_SIZE_CHANGED) {
+        // In practice, it seems to always be called from the same thread in
+        // that specific case. Anyway, it's just a workaround.
+        screen_handle_window_event(&screen, &event->window);
     }
     return 0;
 }
@@ -127,6 +128,7 @@ enum event_result {
     EVENT_RESULT_CONTINUE,
     EVENT_RESULT_STOPPED_BY_USER,
     EVENT_RESULT_STOPPED_BY_EOS,
+    EVENT_RESULT_STOPPED_BY_ERROR,
 };
 
 static enum event_result
@@ -149,7 +151,9 @@ handle_event(SDL_Event *event, bool control) {
             }
             break;
         case SDL_WINDOWEVENT:
-            screen_handle_window_event(&screen, &event->window);
+            if (!screen_handle_window_event(&screen, &event->window)) {
+                return EVENT_RESULT_STOPPED_BY_ERROR;
+            }
             break;
         case SDL_TEXTINPUT:
             if (!control) {
@@ -221,6 +225,9 @@ event_loop(bool display, bool control) {
             case EVENT_RESULT_STOPPED_BY_EOS:
                 LOGW("Device disconnected");
                 return false;
+            case EVENT_RESULT_STOPPED_BY_ERROR:
+                LOGC("Stopping due to unrecoverable error");
+                return false;
             case EVENT_RESULT_CONTINUE:
                 break;
         }

app/src/screen.c

@@ -113,6 +113,13 @@ get_optimal_size(struct size current_size, struct size content_size) {
         h = MIN(current_size.height, display_size.height);
     }
 
+    if (h == w * content_size.height / content_size.width
+     || w == h * content_size.width / content_size.height) {
+        // The size is already optimal, if we ignore rounding errors due to
+        // integer window dimensions
+        return (struct size) {w, h};
+    }
+
     bool keep_width = content_size.width * h > content_size.height * w;
     if (keep_width) {
         // remove black borders on top and bottom
@@ -210,10 +217,9 @@ screen_init_rendering(struct screen *screen, const char *window_title,
 
     struct size window_size =
         get_initial_optimal_size(content_size, window_width, window_height);
-    uint32_t window_flags = SDL_WINDOW_HIDDEN | SDL_WINDOW_RESIZABLE;
-#ifdef HIDPI_SUPPORT
-    window_flags |= SDL_WINDOW_ALLOW_HIGHDPI;
-#endif
+    uint32_t window_flags = SDL_WINDOW_HIDDEN
+                          | SDL_WINDOW_RESIZABLE
+                          | SDL_WINDOW_ALLOW_HIGHDPI;
     if (always_on_top) {
 #ifdef SCRCPY_SDL_HAS_WINDOW_ALWAYS_ON_TOP
         window_flags |= SDL_WINDOW_ALWAYS_ON_TOP;
@@ -258,7 +264,7 @@ screen_init_rendering(struct screen *screen, const char *window_title,
         return false;
     }
 
-    // stats with "opengl"
+    // starts with "opengl"
     screen->use_opengl = renderer_name && !strncmp(renderer_name, "opengl", 6);
     if (screen->use_opengl) {
         struct sc_opengl *gl = &screen->gl;
@@ -303,6 +309,11 @@ screen_init_rendering(struct screen *screen, const char *window_title,
 
     screen->windowed_window_size = window_size;
 
+    struct scale_ratio *rw = &screen->scale.w;
+    struct scale_ratio *rh = &screen->scale.h;
+    SDL_GetWindowSize(screen->window, &rw->window, &rh->window);
+    SDL_GL_GetDrawableSize(screen->window, &rw->drawable, &rh->drawable);
+
     return true;
 }
 
@@ -512,11 +523,74 @@ screen_resize_to_pixel_perfect(struct screen *screen) {
                                             content_size.height);
 }
 
-void
+bool
+screen_fix_hidpi(struct screen *screen) {
+    // If the scale ratio has changed, recreate the renderer to fix HiDPI issues
+    // <https://github.com/Genymobile/scrcpy/issues/15>
+
+    int ww, wh, dw, dh;
+    SDL_GetWindowSize(screen->window, &ww, &wh);
+    SDL_GL_GetDrawableSize(screen->window, &dw, &dh);
+
+    struct scale_ratio *rw = &screen->scale.w;
+    struct scale_ratio *rh = &screen->scale.h;
+
+    if (ww * rw->drawable == dw * rw->window &&
+        wh * rh->drawable == dh * rh->window) {
+        // same ratio, both horizontally and vertically, nothing to do
+        return true;
+    }
+
+    // update the current scale
+    rw->window = ww;
+    rh->window = wh;
+    rw->drawable = dw;
+    rh->drawable = dh;
+
+    if (screen->texture) {
+        SDL_DestroyTexture(screen->texture);
+    }
+    if (screen->renderer) {
+        SDL_DestroyRenderer(screen->renderer);
+    }
+
+    screen->renderer = SDL_CreateRenderer(screen->window, -1,
+                                          SDL_RENDERER_ACCELERATED);
+    if (!screen->renderer) {
+        LOGC("Could not create renderer: %s", SDL_GetError());
+        return false;
+    }
+
+    struct size content_size = screen->content_size;
+    if (SDL_RenderSetLogicalSize(screen->renderer, content_size.width,
+                                 content_size.height)) {
+        LOGE("Could not set renderer logical size: %s", SDL_GetError());
+        SDL_DestroyRenderer(screen->renderer);
+        return false;
+    }
+
+    // FIXME this is wrong, we must update the last frame to the new texture,
+    // but we don't have it anymore!
+    screen->texture = create_texture(screen);
+    if (!screen->texture) {
+        LOGC("Could not create texture: %s", SDL_GetError());
+        SDL_DestroyRenderer(screen->renderer);
+        return false;
+    }
+
+    LOGD("Renderer and texture reset");
+    return true;
+}
+
+bool
 screen_handle_window_event(struct screen *screen,
                            const SDL_WindowEvent *event) {
     switch (event->event) {
         case SDL_WINDOWEVENT_EXPOSED:
+            if (!screen_fix_hidpi(screen)) {
+                // unrecoverable
+                return false;
+            }
             screen_render(screen);
             break;
         case SDL_WINDOWEVENT_SIZE_CHANGED:
@@ -552,6 +626,8 @@ screen_handle_window_event(struct screen *screen,
             apply_windowed_size(screen);
             break;
     }
+
+    return true;
 }
 
 struct point

app/src/screen.h

@@ -13,6 +13,11 @@
 
 struct video_buffer;
 
+struct scale_ratio {
+    int window;
+    int drawable;
+};
+
 struct screen {
     SDL_Window *window;
     SDL_Renderer *renderer;
@@ -33,6 +38,11 @@ struct screen {
     bool maximized;
     bool no_window;
     bool mipmaps;
+
+    struct {
+        struct scale_ratio w;
+        struct scale_ratio h;
+    } scale;
 };
 
 #define SCREEN_INITIALIZER { \
@@ -63,6 +73,16 @@ struct screen {
     .maximized = false, \
     .no_window = false, \
     .mipmaps = false, \
+    .scale = { \
+        .w = { \
+            .window = 0, \
+            .drawable = 0, \
+        }, \
+        .h = { \
+            .window = 0, \
+            .drawable = 0, \
+        }, \
+    } \
 }
 
 // initialize default values
@@ -111,7 +131,8 @@ void
 screen_set_rotation(struct screen *screen, unsigned rotation);
 
 // react to window events
-void
+// return true on success, false on unrecoverable error
+bool
 screen_handle_window_event(struct screen *screen, const SDL_WindowEvent *event);
 
 // convert point from window coordinates to frame coordinates

meson_options.txt

@@ -4,6 +4,5 @@ option('crossbuild_windows', type: 'boolean', value: false, description: 'Build
 option('windows_noconsole', type: 'boolean', value: false, description: 'Disable console on Windows (pass -mwindows flag)')
 option('prebuilt_server', type: 'string', description: 'Path of the prebuilt server')
 option('portable', type: 'boolean', value: false, description: 'Use scrcpy-server from the same directory as the scrcpy executable')
-option('hidpi_support', type: 'boolean', value: true, description: 'Enable High DPI support')
 option('server_debugger', type: 'boolean', value: false, description: 'Run a server debugger and wait for a client to be attached')
 option('server_debugger_method', type: 'combo', choices: ['old', 'new'], value: 'new', description: 'Select the debugger method (Android < 9: "old", Android >= 9: "new")')